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Afternoon exercise was associated with greater fat loss than morning exercise in overweight/obese adults with the PER3 rs228697 CC genotype

In an 8-week supervised moderate-intensity continuous training (MICT) intervention, overweight/obese university students with the PER3 rs228697 CC genotype who exercised in the afternoon (16:00-19:00) showed descriptively larger reductions in body weight, BMI, waist circumference, body fat percentage, and total fat mass compared to those who exercised in the morning (7:00-10:00). However, the between-group differences were modest and imprecise, and the study was exploratory, so strong conclusions cannot be drawn.

Last updated: Aug 20, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score34/100
Human RCT☆☆☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Afternoon exercise was associated with greater fat loss than morning exercise in overweight/obese adults: an exploratory study of PER3 rs228697 genotype matching.

observational

Wang Y, Xu C, Tong J · Frontiers in physiology (2026)

Participants: N/A
Duration: 8 weeks
Intervention: Morning (7:00-10:00) vs. afternoon (16:00-19:00) moderate-intensity continuous training (MICT) for 8 weeks
Outcome: Body weight, BMI, waist circumference, body fat percentage, total fat mass, regional fat mass (trunk, android, gynoid)
Effect Size: N/A (descriptive differences only, no effect size reported)
Population: Overweight/obese university students (n=31) with PER3 rs228697 CC genotype or G-allele carriers

Result:

PubMed: 42597286DOI: 10.3389/fphys.2026.1872652

Mechanism Graph

Exercise timing may influence circadian metabolic rhythms
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PER3 rs228697 polymorphism may affect chronotype and metabolic responses
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Afternoon exercise may align better with circadian peaks in metabolism and fat oxidation
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Result: Greater fat loss in afternoon exercise group among CC genotype carriers

Limitations

  • ⚠Small sample size (n=31) and very small G-allele carrier subgroup (G-PM) limiting interpretability
  • ⚠Exploratory design with no randomization to genotype groups; estimates were imprecise
  • ⚠No objective circadian phenotyping; behavioral chronotype did not correspond with PER3 genotype

Frequently Asked Questions

What is the PER3 rs228697 polymorphism?▼

It is a genetic variant in the PER3 gene, which is part of the circadian clock system, and has been linked to chronotype-related traits.

Did afternoon exercise lead to greater fat loss than morning exercise?▼

In this exploratory study, among participants with the CC genotype, afternoon exercise showed descriptively larger reductions in body composition measures, but the differences were not statistically robust.

Who were the participants in this study?▼

Overweight/obese university students, with a total of 31 participants, who performed 8 weeks of supervised moderate-intensity continuous training.

Can I use this study to decide when to exercise for weight loss?▼

The study is exploratory and has limitations, so it does not provide strong evidence for genotype-based exercise timing. Larger, well-controlled studies are needed before making personalized recommendations.

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References

  1. 1.Wang Y, Xu C, Tong J. "Afternoon exercise was associated with greater fat loss than morning exercise in overweight/obese adults: an exploratory study of PER3 rs228697 genotype matching.." Frontiers in physiology, 2026. PMID: 42597286 DOI: 10.3389/fphys.2026.1872652
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.